The present invention is directed to a vehicular lamp, and more particularly to a vehicular lamp having a seal groove extending along the entire periphery of a front opening of the lamp body for mounting a front lens to the front opening. The invention also relates to a machine and method for manufacturing the same.
A conventional vehicular lamp is constituted by a lamp body in which is mounted a reflector, a light bulb and the like, an outer lens covering the front opening of the lamp body, and a seal groove formed in an outer peripheral part of the front opening of the lamp body extending along the peripheral part. With this structure, during assembly, a seal leg formed on the peripheral portion of the outer lens is inserted into the seal groove, and then the seal groove is filled with a sealing material such as a hot melt or the like. The outer lens is then fixedly coupled to the lamp body by hardening the sealing material.
FIG. 7 is a partially exploded perspective view of a conventional lamp of this type. As shown in FIG. 7, a shelf member 14, which is L-shaped in cross section, is integrally formed with a lamp body 1 on an outer peripheral part 11a of the front opening 11 thereof. A concave seal groove 15 is formed between the outer peripheral part 11a of the lamp body 1 and the shelf member 14. During the assembly of the lamp, a seal leg 52 of the outer lens 5 is inserted into the seal groove 15 to couple the lens 5 with the lamp body 1, and the outer lens 5 is secured thereto by filling and hardening a sealing material (not shown) filling the seal groove 15.
The inner surface of the lamp body is made reflective to form a reflector by coating thereon a thin layer of aluminum, depositing aluminum or the like. A bulb 3, supported inside the lamp body 1 by a bulb socket 2, emits light which is reflected by the reflector to thus provide a desired light distribution pattern.
The lamp body 1 thus constituted is generally formed integrally by a molding process. When the lamp body is actually molded, the junction 14a of the peripheral part 11a of the front opening 11 and the shelf member 14 for defining the seal groove 15 is thickened, that is, the volume of resin at the junction 14a becomes large. Therefore, the surface X of the junction portion cools earlier than other portions, and when the inside is cooled, the surface X of the junction portion undesirably sinks because the volume at the portion is shrunk.
FIG. 8 is an enlarged cross-sectional view of the conventional lamp taken along line XIII--XIII in FIG. 7 illustrating the condition where shrinkage at the surface X is generated on an inner surface of the lamp body 1 in areas corresponding to the seal groove. The shrinkage X extends along the entire periphery of the front opening 11, thereby degrading the external appearance of the lamp since the linear shrinkage region can be viewed from the outside through the outer lens.
Particularly, in the case where the inner surface of the lamp body 1 forms the reflector, since a small concave/convex condition on the reflector can cause a relatively large alteration in the reflected light pattern, the shrinkage X becomes particularly conspicuous and the external appearance of the lamp is accordingly seriously deteriorated.
Further, for a lamp having a substantially transparent clear lens in which no lens steps are formed, as has recently become common, the shrinkage X is quite conspicuous when viewed through the lens 5.
Furthermore, if shrinkage X, that is, a concave/convex condition, is formed on the inner bottom surface of the seal groove 15, the flow of the sealing material tends to stagnate in such regions when the seal groove is filled with sealing material. As a result, air bubbles may be generated, thereby decreasing the mounting strength of the outer lens by the sealing material and also decreasing the sealability at the mounting portion.